src/odhcpd.c

   1 /**
   2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License v2 as published by
   6  * the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  */
  14
  15 #include <time.h>
  16 #include <errno.h>
  17 #include <fcntl.h>
  18 #include <stdio.h>
  19 #include <resolv.h>
  20 #include <getopt.h>
  21 #include <stddef.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <signal.h>
  26 #include <stdbool.h>
  27
  28 #include <arpa/inet.h>
  29 #include <net/if.h>
  30 #include <netinet/ip6.h>
  31 #include <netpacket/packet.h>
  32 #include <linux/rtnetlink.h>
  33
  34 #include <sys/socket.h>
  35 #include <sys/ioctl.h>
  36 #include <sys/epoll.h>
  37 #include <sys/types.h>
  38 #include <sys/wait.h>
  39 #include <sys/syscall.h>
  40
  41 #include <libubox/uloop.h>
  42 #include "odhcpd.h"
  43
  44
  45
  46 static int ioctl_sock;
  47 static int rtnl_socket = -1;
  48 static int rtnl_seq = 0;
  49 static int urandom_fd = -1;
  50
  51
  52 static void sighandler(_unused int signal)
  53 {
  54         uloop_end();
  55 }
  56
  57
  58 int main()
  59 {
  60         openlog("odhcpd", LOG_PERROR | LOG_PID, LOG_DAEMON);
  61         setlogmask(LOG_UPTO(LOG_WARNING));
  62         uloop_init();
  63
  64         if (getuid() != 0) {
  65                 syslog(LOG_ERR, "Must be run as root!");
  66                 return 2;
  67         }
  68
  69         ioctl_sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
  70
  71         if ((rtnl_socket = odhcpd_open_rtnl()) < 0) {
  72                 syslog(LOG_ERR, "Unable to open socket: %s", strerror(errno));
  73                 return 2;
  74         }
  75
  76         if ((urandom_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC)) < 0)
  77                 return 4;
  78
  79         signal(SIGUSR1, SIG_IGN);
  80         signal(SIGINT, sighandler);
  81         signal(SIGTERM, sighandler);
  82
  83         if (init_router())
  84                 return 4;
  85
  86         if (init_dhcpv6())
  87                 return 4;
  88
  89         if (init_ndp())
  90                 return 4;
  91
  92         if (init_dhcpv4())
  93                 return 4;
  94
  95         odhcpd_run();
  96         return 0;
  97 }
  98
  99 int odhcpd_open_rtnl(void)
 100 {
 101         int sock = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
 102
 103         // Connect to the kernel netlink interface
 104         struct sockaddr_nl nl = {.nl_family = AF_NETLINK};
 105         if (connect(sock, (struct sockaddr*)&nl, sizeof(nl))) {
 106                 syslog(LOG_ERR, "Failed to connect to kernel rtnetlink: %s",
 107                                 strerror(errno));
 108                 return -1;
 109         }
 110
 111         return sock;
 112 }
 113
 114
 115 // Read IPv6 MTU for interface
 116 int odhcpd_get_interface_mtu(const char *ifname)
 117 {
 118         char buf[64];
 119         const char *sysctl_pattern = "/proc/sys/net/ipv6/conf/%s/mtu";
 120         snprintf(buf, sizeof(buf), sysctl_pattern, ifname);
 121
 122         int fd = open(buf, O_RDONLY);
 123         ssize_t len = read(fd, buf, sizeof(buf) - 1);
 124         close(fd);
 125
 126         if (len < 0)
 127                 return -1;
 128
 129
 130         buf[len] = 0;
 131         return atoi(buf);
 132
 133 }
 134
 135
 136 // Read IPv6 MAC for interface
 137 int odhcpd_get_mac(const struct interface *iface, uint8_t mac[6])
 138 {
 139         struct ifreq ifr;
 140         memset(&ifr, 0, sizeof(ifr));
 141         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
 142         if (ioctl(ioctl_sock, SIOCGIFHWADDR, &ifr) < 0)
 143                 return -1;
 144         memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
 145         return 0;
 146 }
 147
 148
 149 // Forwards a packet on a specific interface
 150 ssize_t odhcpd_send(int socket, struct sockaddr_in6 *dest,
 151                 struct iovec *iov, size_t iov_len,
 152                 const struct interface *iface)
 153 {
 154         // Construct headers
 155         uint8_t cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))] = {0};
 156         struct msghdr msg = {(void*)dest, sizeof(*dest), iov, iov_len,
 157                                 cmsg_buf, sizeof(cmsg_buf), 0};
 158
 159         // Set control data (define destination interface)
 160         struct cmsghdr *chdr = CMSG_FIRSTHDR(&msg);
 161         chdr->cmsg_level = IPPROTO_IPV6;
 162         chdr->cmsg_type = IPV6_PKTINFO;
 163         chdr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
 164         struct in6_pktinfo *pktinfo = (struct in6_pktinfo*)CMSG_DATA(chdr);
 165         pktinfo->ipi6_ifindex = iface->ifindex;
 166
 167         // Also set scope ID if link-local
 168         if (IN6_IS_ADDR_LINKLOCAL(&dest->sin6_addr)
 169                         || IN6_IS_ADDR_MC_LINKLOCAL(&dest->sin6_addr))
 170                 dest->sin6_scope_id = iface->ifindex;
 171
 172         // IPV6_PKTINFO doesn't really work for IPv6-raw sockets (bug?)
 173         if (dest->sin6_port == 0) {
 174                 msg.msg_control = NULL;
 175                 msg.msg_controllen = 0;
 176         }
 177
 178         char ipbuf[INET6_ADDRSTRLEN];
 179         inet_ntop(AF_INET6, &dest->sin6_addr, ipbuf, sizeof(ipbuf));
 180
 181         ssize_t sent = sendmsg(socket, &msg, MSG_DONTWAIT);
 182         if (sent < 0)
 183                 syslog(LOG_NOTICE, "Failed to send to %s%%%s (%s)",
 184                                 ipbuf, iface->ifname, strerror(errno));
 185         else
 186                 syslog(LOG_DEBUG, "Sent %li bytes to %s%%%s",
 187                                 (long)sent, ipbuf, iface->ifname);
 188         return sent;
 189 }
 190
 191
 192 // Detect an IPV6-address currently assigned to the given interface
 193 ssize_t odhcpd_get_interface_addresses(int ifindex,
 194                 struct odhcpd_ipaddr *addrs, size_t cnt)
 195 {
 196         struct {
 197                 struct nlmsghdr nhm;
 198                 struct ifaddrmsg ifa;
 199         } req = {{sizeof(req), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
 200                         ++rtnl_seq, 0}, {AF_INET6, 0, 0, 0, ifindex}};
 201         if (send(rtnl_socket, &req, sizeof(req), 0) < (ssize_t)sizeof(req))
 202                 return 0;
 203
 204         uint8_t buf[8192];
 205         ssize_t len = 0, ret = 0;
 206
 207         for (struct nlmsghdr *nhm = NULL; ; nhm = NLMSG_NEXT(nhm, len)) {
 208                 while (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 209                         len = recv(rtnl_socket, buf, sizeof(buf), 0);
 210                         nhm = (struct nlmsghdr*)buf;
 211                         if (len < 0 || !NLMSG_OK(nhm, (size_t)len)) {
 212                                 if (errno == EINTR)
 213                                         continue;
 214                                 else
 215                                         return ret;
 216                         }
 217                 }
 218
 219                 if (nhm->nlmsg_type != RTM_NEWADDR)
 220                         break;
 221
 222                 // Skip address but keep clearing socket buffer
 223                 if (ret >= (ssize_t)cnt)
 224                         continue;
 225
 226                 struct ifaddrmsg *ifa = NLMSG_DATA(nhm);
 227                 if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
 228                                 (ifindex && ifa->ifa_index != (unsigned)ifindex))
 229                         continue;
 230
 231                 struct rtattr *rta = (struct rtattr*)&ifa[1];
 232                 size_t alen = NLMSG_PAYLOAD(nhm, sizeof(*ifa));
 233                 memset(&addrs[ret], 0, sizeof(addrs[ret]));
 234                 addrs[ret].prefix = ifa->ifa_prefixlen;
 235
 236                 while (RTA_OK(rta, alen)) {
 237                         if (rta->rta_type == IFA_ADDRESS) {
 238                                 memcpy(&addrs[ret].addr, RTA_DATA(rta),
 239                                                 sizeof(struct in6_addr));
 240                         } else if (rta->rta_type == IFA_CACHEINFO) {
 241                                 struct ifa_cacheinfo *ifc = RTA_DATA(rta);
 242                                 addrs[ret].preferred = ifc->ifa_prefered;
 243                                 addrs[ret].valid = ifc->ifa_valid;
 244                         }
 245
 246                         rta = RTA_NEXT(rta, alen);
 247                 }
 248
 249                 if (ifa->ifa_flags & IFA_F_DEPRECATED)
 250                         addrs[ret].preferred = 0;
 251
 252                 addrs[ret].has_class = false;
 253                 addrs[ret].class = 0;
 254 #ifdef WITH_UBUS
 255                 struct interface *iface = odhcpd_get_interface_by_index(ifindex);
 256                 if (iface)
 257                         addrs[ret].has_class = ubus_get_class(iface->ifname,
 258                                         &addrs[ret].addr, &addrs[ret].class);
 259 #endif
 260                 ++ret;
 261         }
 262
 263         return ret;
 264 }
 265
 266
 267 struct interface* odhcpd_get_interface_by_index(int ifindex)
 268 {
 269         struct interface *iface;
 270         list_for_each_entry(iface, &interfaces, head)
 271                 if (iface->ifindex == ifindex)
 272                         return iface;
 273
 274         return NULL;
 275 }
 276
 277
 278 struct interface* odhcpd_get_interface_by_name(const char *name)
 279 {
 280         struct interface *iface;
 281         list_for_each_entry(iface, &interfaces, head)
 282                 if (!strcmp(iface->ifname, name))
 283                         return iface;
 284
 285         return NULL;
 286 }
 287
 288
 289 struct interface* odhcpd_get_master_interface(void)
 290 {
 291         struct interface *iface;
 292         list_for_each_entry(iface, &interfaces, head)
 293                 if (iface->master)
 294                         return iface;
 295
 296         return NULL;
 297 }
 298
 299
 300 // Convenience function to receive and do basic validation of packets
 301 static void odhcpd_receive_packets(struct uloop_fd *u, _unused unsigned int events)
 302 {
 303         struct odhcpd_event *e = container_of(u, struct odhcpd_event, uloop);
 304
 305         uint8_t data_buf[RELAYD_BUFFER_SIZE], cmsg_buf[128];
 306         union {
 307                 struct sockaddr_in6 in6;
 308                 struct sockaddr_in in;
 309                 struct sockaddr_ll ll;
 310                 struct sockaddr_nl nl;
 311         } addr;
 312
 313         while (true) {
 314                 struct iovec iov = {data_buf, sizeof(data_buf)};
 315                 struct msghdr msg = {&addr, sizeof(addr), &iov, 1,
 316                                 cmsg_buf, sizeof(cmsg_buf), 0};
 317
 318                 ssize_t len = recvmsg(u->fd, &msg, MSG_DONTWAIT);
 319                 if (len < 0) {
 320                         if (errno == EAGAIN)
 321                                 break;
 322                         else
 323                                 continue;
 324                 }
 325
 326
 327                 // Extract destination interface
 328                 int destiface = 0;
 329                 int *hlim = NULL;
 330                 void *dest = NULL;
 331                 struct in6_pktinfo *pktinfo;
 332                 struct in_pktinfo *pkt4info;
 333                 for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; ch = CMSG_NXTHDR(&msg, ch)) {
 334                         if (ch->cmsg_level == IPPROTO_IPV6 &&
 335                                         ch->cmsg_type == IPV6_PKTINFO) {
 336                                 pktinfo = (struct in6_pktinfo*)CMSG_DATA(ch);
 337                                 destiface = pktinfo->ipi6_ifindex;
 338                                 dest = &pktinfo->ipi6_addr;
 339                         } else if (ch->cmsg_level == IPPROTO_IP &&
 340                                         ch->cmsg_type == IP_PKTINFO) {
 341                                 pkt4info = (struct in_pktinfo*)CMSG_DATA(ch);
 342                                 destiface = pkt4info->ipi_ifindex;
 343                                 dest = &pkt4info->ipi_addr;
 344                         } else if (ch->cmsg_level == IPPROTO_IPV6 &&
 345                                         ch->cmsg_type == IPV6_HOPLIMIT) {
 346                                 hlim = (int*)CMSG_DATA(ch);
 347                         }
 348                 }
 349
 350                 // Check hoplimit if received
 351                 if (hlim && *hlim != 255)
 352                         continue;
 353
 354                 // Detect interface for packet sockets
 355                 if (addr.ll.sll_family == AF_PACKET)
 356                         destiface = addr.ll.sll_ifindex;
 357
 358                 struct interface *iface =
 359                                 odhcpd_get_interface_by_index(destiface);
 360
 361                 if (!iface && addr.nl.nl_family != AF_NETLINK)
 362                         continue;
 363
 364                 char ipbuf[INET6_ADDRSTRLEN] = "kernel";
 365                 if (addr.ll.sll_family == AF_PACKET &&
 366                                 len >= (ssize_t)sizeof(struct ip6_hdr))
 367                         inet_ntop(AF_INET6, &data_buf[8], ipbuf, sizeof(ipbuf));
 368                 else if (addr.in6.sin6_family == AF_INET6)
 369                         inet_ntop(AF_INET6, &addr.in6.sin6_addr, ipbuf, sizeof(ipbuf));
 370                 else if (addr.in.sin_family == AF_INET)
 371                         inet_ntop(AF_INET, &addr.in.sin_addr, ipbuf, sizeof(ipbuf));
 372
 373                 syslog(LOG_DEBUG, "--");
 374                 syslog(LOG_DEBUG, "Received %li Bytes from %s%%%s", (long)len,
 375                                 ipbuf, (iface) ? iface->ifname : "netlink");
 376
 377                 e->handle_dgram(&addr, data_buf, len, iface, dest);
 378         }
 379 }
 380
 381 // Register events for the multiplexer
 382 int odhcpd_register(struct odhcpd_event *event)
 383 {
 384         event->uloop.cb = odhcpd_receive_packets;
 385         return uloop_fd_add(&event->uloop, ULOOP_READ);
 386 }
 387
 388 void odhcpd_process(struct odhcpd_event *event)
 389 {
 390         odhcpd_receive_packets(&event->uloop, 0);
 391 }
 392
 393 void odhcpd_urandom(void *data, size_t len)
 394 {
 395         read(urandom_fd, data, len);
 396 }
 397
 398
 399 time_t odhcpd_time(void)
 400 {
 401         struct timespec ts;
 402         syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts);
 403         return ts.tv_sec;
 404 }
 405
 406
 407 static const char hexdigits[] = "0123456789abcdef";
 408 static const int8_t hexvals[] = {
 409     -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1,
 410     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 411     -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 412      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
 413     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 414     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 415     -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 416     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
 417 };
 418
 419 ssize_t odhcpd_unhexlify(uint8_t *dst, size_t len, const char *src)
 420 {
 421         size_t c;
 422         for (c = 0; c < len && src[0] && src[1]; ++c) {
 423                 int8_t x = (int8_t)*src++;
 424                 int8_t y = (int8_t)*src++;
 425                 if (x < 0 || (x = hexvals[x]) < 0
 426                                 || y < 0 || (y = hexvals[y]) < 0)
 427                         return -1;
 428                 dst[c] = x << 4 | y;
 429                 while (((int8_t)*src) < 0 ||
 430                                 (*src && hexvals[(uint8_t)*src] < 0))
 431                         src++;
 432         }
 433
 434         return c;
 435 }
 436
 437
 438 void odhcpd_hexlify(char *dst, const uint8_t *src, size_t len)
 439 {
 440         for (size_t i = 0; i < len; ++i) {
 441                 *dst++ = hexdigits[src[i] >> 4];
 442                 *dst++ = hexdigits[src[i] & 0x0f];
 443         }
 444         *dst = 0;
 445 }
 446
 447
 448 int odhcpd_bmemcmp(const void *av, const void *bv, size_t bits)
 449 {
 450         const uint8_t *a = av, *b = bv;
 451         size_t bytes = bits / 8;
 452         bits %= 8;
 453
 454         int res = memcmp(a, b, bytes);
 455         if (res == 0 && bits > 0)
 456                 res = (a[bytes] >> (8 - bits)) - (b[bytes] >> (8 - bits));
 457
 458         return res;
 459 }
 460
 461
 462 void odhcpd_bmemcpy(void *av, const void *bv, size_t bits)
 463 {
 464         uint8_t *a = av;
 465         const uint8_t *b = bv;
 466
 467         size_t bytes = bits / 8;
 468         bits %= 8;
 469         memcpy(a, b, bytes);
 470
 471         if (bits > 0) {
 472                 uint8_t mask = (1 << (8 - bits)) - 1;
 473                 a[bytes] = (a[bytes] & mask) | ((~mask) & b[bytes]);
 474         }
 475 }